Preheat the oven to 400°F.
In a shallow baking dish, coat the steaks in oil, salt and pepper. Rest for 10 minutes.
On a baking sheet, toss the sweet potatoes with the oil, salt and pepper. Roast for 16-20 minutes, or until tender.
Preheat the grill or a large skillet over high heat.
Grill the steaks for 3 to 4 minutes per side to sear, then lower the heat to medium and cook until an instant-read thermometer reaches 130°F for rare, 140°F for medium rare and 150°F for medium-well.
Transfer the grilled steaks to a cutting board and rest for 5 to 10 minutes, then slice against the grain.
Combine all of the tomato salad ingredients in a bowl. Season to taste.
Add all of the chimichurri ingredients except the oil to a blender. Purée until smooth. With the motor running, drizzle in the oil until emulsified. Season to taste.
Divide the steaks and sweet potatoes between plates. Serve with tomato salad and drizzle with chimichurri.